well, it got you to a national title, so whatever combo you and your trainer had going on it worked.
The trainer/boxer partnership for me, can only really work if there is trust.

I don't think your other trainer is a fraud, he has a different approach & understanding of the sport to this other guy.
I suspect as you've learnt more and become more critical in to the hows and whys of your boxing this other trainer has brought something new to your arsenal.

I take it from this you'll be changing camps? Just don't burn any bridges in case it doesn't work out